Device for measuring the frequency of rotation of a vehicle wheel

ABSTRACT

A device for measuring the frequency of rotation of a vehicle wheel comprises a toothed wheel rotatable with the vehicle wheel, and an electromagnetic pick-up winding past which in use the teeth move to produce pulses in the winding. The toothed wheel is provided with a layer of non-magnetic material which covers the crown of each tooth, the pick-up winding moving over the layer of the non-magnetic material and being resiliently urged towards the toothed wheel so as not to be disengaged from the layer in use. The arrangement of the layer of non-magnetic material is such that the winding remains at a constant distance from the teeth as the winding moves over the layer.

United States Patent 1 Phoenix et a1.

11 3,745,32 [4 1 Jui 10,1973

[ DEVICE FOR MEASURING THE FREQUENCY OF ROTATION OF A VEHICLE WHEEL [75]Inventors: Lancelot Phoenix, Handsworth Wood; David Valentine Walpole,Hall Green, both of England [30] Foreign Application Priority Data Nov.10, 1969 Great Britain..' 54,872/69 June 13, 1970 Great Britain28,746/70 [52] US. Cl. 310/168, 324/173 [51] Int. Cl. G0lp 3/48 Field ofSearch 324/173, 174, 163, 324/34 GT, 34 P, 34 D; 310/86, 155, 168;

340/263; 303/21 EB, 21 CF, 21 CG, 21 P, 21

lNJ TEl/ME/VT 3,653,471 4/1972 Burckhardt 324/174 3,489,935 l/1970 Hayes310/168 3,551,712 12/1970 Jones 310/168 3,482,129 12/1969 Riordan310/168 FOREIGN PATENTS OR APPLICATIONS 1,088,106 10/1967 Great Britain324/174 Primary Examiner-Michael J. Lynch Attorney-Holman & Stern [5 7]ABSTRACT A device for measuring the frequency of rotation of a vehiclewheel comprises a toothed wheel rotatable with the vehicle wheel, and anelectromagnetic pick-up winding past which in use the teeth move toproduce pulses in the winding. The toothed wheel is provided with alayer of non-magnetic material which covers the crown of each tooth, thepick-up winding moving over the layer of the non-magnetic material andbeing resiliently urged towards the toothed wheel so as not to bedisengaged from the layer in use. The arrangement of the layer ofnon-magnetic material is such that the winding remains at a constantdistance from the teeth as the winding moves over the layer.

8 Claims, 4 Drawing Figures PATENTELJ'JUO'W 2.745.392 sum 1 ur 2 DEVICEFOR MEASURING THE FREQUENCY OF ROTATION OF A VEHICLE WHEEL Thisinvention relates to a device for measuring the frequency of rotation ofa vehicle wheel.

A device according to the invention comprises a toothed wheel rotatablewith the vehicle wheel, and an electromagnetic pick-up winding pastwhich in use the teeth move to produce pulses in said winding, thetoothed wheel being provided with a layer of nonmagnetic material whichcovers the crown of each tooth, the pick-up winding moving over saidlayer of the non-magnetic material and being resiliently urged towardssaid toothed wheel so as not to be disengaged from said layer in use,the arrangement of said layer being such that said winding remains at aconstant distance from the teeth as the winding moves over said layer.

In the accompanying drawings:

FIG. 1 is a sectional view of a frequency sensing device according toone example of the invention when mounted on the axle of a wheel of aroad vehicle,

FIG. 2 is a sectional view of FIG. 1,

FIG. 3 is a diagrammatic representation of a frequency sensing deviceaccording to a second example of the invention, and

FIG. 4 is a plan view of a frequency sensing device according to a thirdexample of the invention.

Referring to FIGS. 1 and 2, a frequency sensing device includes anannular, externally toothed wheel 11, the wheel being accuratelymachined so that there is a fixed, predetermined distance betweenadjacent teeth 12 on the wheel and also so that the crowns 13 of theteeth 12 define an external cylindrical surface. A layer 14 ofnon-magnetic material having a low coefficient of friction such as glassfilled nylon is moulded around the teeth 12 of the wheel 11 so as tofill the gaps between the teeth and cover the crowns of the teeth. Thelayer 14 is then machined so that there is an even thickness of thefilled nylon over the crown of each of the teeth 12 and so that theperiphery of the layer 14 is cylindrical and co-axial with the wheel 11.In the example shown, the wheel 11 is mounted on the axle 15 of a wheel10 of a road vehicle for rotation therewith and a sensing instrument 16is mounted adjacent the layer 14 so as to move over the layer 14 as thewheel 11 rotates in use. The instrument 16 is supported in nonmagnetic,synthetic resin moulding 17 preferably fonned of a material having a lowcoefficient of friction such as glass filled nylon, the moulding 17engaging the layer 14 and the wheel 11 being free to rotate relative tothe moulding 17 and the instrument 16. The moulding 17 is supported in atwo-part, annular casing 18 by a pair of lugs 19 integral with thecasing 18, the lugs being engaged in a pair of recesses 21 respectivelyformed in opposite sides of the moulding 17. The moulding 17 isresiliently urged towards the toothed wheel 11 by a spring blade 22, thedimensions of the recesses 21 being such that the moulding 17 is capableof movement relative to the lugs towards and away from the wheel 1 1.Thus, the moulding 17 remains in contact with the layer 14 duringrotation of the wheel 11 despite any small eccentricities which may bepresent in the layer 14. As shown in FIG. 1, the casing 18 is mounted onthe brake back plate 23 of the vehicle wheel 10 by a locating peg 24integral with the casing 18. The brake back plate 23 is of course,movable vertically with the axle 15 so that the moulding 17 is urged bythe spring blade 22 to remain in contact with the layer 14 during anyupward or downward movement of the axle 15, that may occur duringrotation. Further the toothed wheel 11 is rotatably mounted in thecasing 18 by a pair of annular ribs 25 integral with the casing 18 andengaging in complementary annular recesses respectively formed inopposite lateral faces of the wheel 11.

The layer 14 of filled nylon is a non-magnetic layer and the sensinginstrument l6 incorporates pick-up winding, so that each time a tooth 12passes the instrument an electrical impulse is produced in the pick-upwinding and is fed by leads 26 extending through the peg 14 to anexternal circuit for measuring the frequency of rotation of the toothedwheel 11 and hence of the vehicle wheel 10.

In a practical embodiment of the above example of the invention, thefrequency sensing instrument is used in an antilock braking system for aroad vehicle, the arrangement being such that if the retardation of thewheel 10 exceeds a predetermined value, corresponding to locking of thebrakes acting on the wheel, then the brakes are automaticallydisengaged. For the antilock brakes to respond quickly to a situationwherein the wheels of the vehicle are locked, it is necessary to have ahigh rate of production of electrical impulses in the pick-up winding ofthe sensing instrument 16. Thus the wheel 11 is required to have a largenumber of teeth, for example 180, so that the gap between adjacent teethis very small and so for accurate sensing of the vehicle wheel speed bythe device, the instrument 16 must be mounted very close to the toothedwheel and at a constant distance from the teeth. Thus a small constantthickness of the non-magnetic material (about 0.015 inch) is formed overthe teeth, and also since the spring blade 22 urges the moulding 17towards the toothed wheel, the gap between the pick-up winding and theteeth is kept small and substantially constant as required.

In a second example of the invention, as illustrated in FIG. 3, thefrequency sensing device includes an internally toothed wheel 31. Sothat the sensing instrument 16 can move over the internal surface of thewheel, the wheel is provided with a peripheral flange 32 in the internalsurface of which the teeth are formed. The wheel 31 is formed in thesame way as in the above example, a sensing instrument 33 beingresiliently urged towards the internal, toothed surface of the wheel andbeing mounted on a support 34 which moves vertically with the vehiclewheel.

FIG. 4 illustrates a third example of the invention in which theconstruction and operation of the sensing device is similar to thosedescribed above, except that the toothed wheel is defined by an annularwheel 35 fonned with an annular row of teeth 36 on one lateral surfaceof the wheel, a sensing instrument 37 moving over the teeth 36.

It is to be appreciated that in the above examples the arrangement ofthe layer 14 of non-magnetic material can be altered so that layer 14extends over the crowns of the teeth and the gaps between the teethwithout actually filling the gaps. Alternatively the layer 14 can bearranged so as to cover only the crown of each tooth, although in thiscase the dimensions of the sensing instrument 16 must be greater thanthe distance between adjacent teeth.

We claim:

1. A device for measuring the frequency of rotation of a vehicle wheelcomprising a toothed wheel rotatable with the vehicle wheel, anelectro-magnetic pickup winding, means mounting the pick-up windingadjacent the toothed wheel so that, in use, the teeth of said wheel movepast the winding to produce pulses in the winding, a layer ofnon-magnetic material covering the crown of each tooth of said wheel,and resilient means urging the pick-up winding towards the toothed wheelso that the pick-up winding is always engaged with said layer ofnon-magnetic material as the teeth of said wheel move past thewinding,the arrangement of said layer being such that the winding remains at aconstant distance from the teeth as the teeth move past the winding.

2. A device as claimed in claim 1 wherein said layer of non-magneticmaterial is arranged to extend over the crowns of the teeth and the gapsbetween the teeth without filling said gaps between the teeth.

- 3. A device as claimed in claim 1 wherein said layer of non-magneticmaterial is arranged to cover the crowns of the teeth and fill the gapsbetween the teeth. I 4. A device as claimed in claim 1 wherein saidtoothed wheel is an externally toothed wheel with said teeth beingformed on the external cylindrical surface of the wheel.

5. A device as claimed in claim 1 wherein said toothed wheel isinternally toothed and includes a peripheral flange in the internalsurface of which said teeth are formed.

6. A device as claimed in claim 1 wherein said teeth are formed as anannular row on one lateral surface of the wheel.

7. A device as claimed in claim 1 wherein a nonmagnetic synthetic resinmoulding supports the pick-up winding.

8. A device for measuring the frequency of rotation of a vehicle wheelcomprising an annular casing, means for mounting the casing on a memberwhich moves vertically with the vehicle wheel, a toothed wheel rotatablymounted in the casing, the toothed wheel being rotatable with thevehicle wheel in use, a layer of nonmagnetic material covering the crownof each tooth of said toothed wheel, a non-magnetic synthetic resinmoulding mounted in the casing, an electro-magnetic pick-up windingsupported by said synthetic resin moulding, means mounting the pick-upwinding adjacent the toothed wheel so that, in use, the teeth of saidwheel move past the winding to produce pulses in the winding, andresilient means urging the moulding into engagement with said layer ofnon-magnetic material so that the moulding always engages said layer asthe teeth of said wheel move past the pick-up winding in use, thearrangement of said layer of non-magnetic material being such that thewinding remains at a constant distance from the teeth as the teeth movepast the pickup winding.

1. A device for measuring the frequency of rotation of a vehicle wheelcomprising a toothed wheel rotatable with the vehicle wheel, anelectro-magnetic pick-up winding, means mounting the pick-up windingadjacent the toothed wheel so that, in use, the teeth of said wheel movepast the winding to produce pulses in the winding, a layer ofnon-magnetic material covering the crown of each tooth of said wheel,and resilient means urging the pickup winding towards the toothed wheelso that the pick-up winding is always engaged with said layer ofnon-magnetic material as the teeth of said wheel move past the winding,the arrangement of said layer being such that the winding remains at aconstant distance from the teeth as the teeth move past the winding. 2.A device as claimed in claim 1 wherein said layer of non-magneticmaterial is arranged to extend over the crowns of the teeth and the gapsbetween the teeth without filling said gaps between the teeth.
 3. Adevice as claimed in claim 1 wherein said layer of non-magnetic materialis arranged to cover the crowns of the teeth and fill the gaps betweenthe teeth.
 4. A device as claimed in claim 1 wherein said toothed wheelis an externally toothed wheel with said teeth being formed on theexternal cylindrical surface of the wheel.
 5. A device as claimed inclaim 1 wherein said toothed wheel is internally toothed and includes aperipheral flange in the internal surface of which said teeth areformed.
 6. A device as claimed in claim 1 wherein said teeth are formedas an annular row on one lateral surface of the wheel.
 7. A device asclaimed in claim 1 wherein a non-magnetic synthetic resin mouldingsupports the pick-up winding.
 8. A device for measuring the frequency ofrotation of a vehicle wheel comprising an annular casing, means formounting the casing on a member which moves vertically with the vehiclewheel, a toothed wheel rotatably mounted in the casing, the toothedwheel being rotatable with the vehicle wheel in use, a layer ofnon-magnetic material covering the crown of each tooth of said toothedwheel, a non-magnetic synthetic resin moulding mounted in the casing, anelectro-magnetic pick-up winding supported by said synthetic resinmoulding, means mounting the pick-up winding adjacent the toothed wheelso that, in use, the teeth of said wheel move past the winding toproduce pulses in the winding, and resilient means urging the mouldinginto engagement with said layer of non-magnetic material so that themoulding always engages said layer as the teeth of said wheel move pastthe pick-up winding in use, the arrangement of said layer ofnon-magnetic material being such that the winding remains at a constantdistance from the teeth as the teeth move past the pick-up winding.